Credential Shield Protocol – Server-blind breach checking for passwords

Show HN: Credential Shield Protocol – Server-blind breach checking for passwords

Credential Shield Protocol – Server-blind breach checking for passwords is a business in show hn launch.

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We're building an open protocol that lets organizations continuously audit credentials against breach databases WITHOUT exposing passwords, full hashes, or query results to any server.The core approach: 1. Hash locally with Argon2 2. Send only first 4 chars of SHA-512 (32-bit prefix) to server 3. Server returns all prefix matches 4. Client verifies locally → server never learns outcomeCurrent state: Protocol spec + threat model + PowerShell client library. We're pre-funding and actively seeking feedback before building the reference implementation.Try it: https://iamaxolotl-04.github.io/csp-2026/ Spec: https://github.com/IAmAxolotl-04/csp-2026We'd love feedback on: - Where does this break in

The company sits in the show hn launch segment, where it competes on its core product or service.

The company is listed at the Show HN launch stage of development.

Website: iamaxolotl-04.github.io/csp-2026